21081047 has 4 divisors (see below), whose sum is σ = 22702680. Its totient is φ = 19459416.

The previous prime is 21081043. The next prime is 21081061. The reversal of 21081047 is 74018012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21081047 - 2² = 21081043 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081043) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 810797 + ... + 810822.

It is an arithmetic number, because the mean of its divisors is an integer number (5675670).

Almost surely, 2^21081047 is an apocalyptic number.

21081047 is a deficient number, since it is larger than the sum of its proper divisors (1621633).

21081047 is a wasteful number, since it uses less digits than its factorization.

21081047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1621632.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 21081047 is about 4591.4101319747. The cubic root of 21081047 is about 276.2468866653.

Adding to 21081047 its reverse (74018012), we get a palindrome (95099059).

The spelling of 21081047 in words is "twenty-one million, eighty-one thousand, forty-seven".